Measuring and controlling apparatus



Aug. 19, 1952 c. A. HARTUNG 2,607,911

MEASURING AND CONTROLLING APPARATus Original Filed Jan. 10, 1947INVENTOR. CHARLES A..HARTUNG WWM ATTQRNEY. W

Patented Aug. 19, 1952 UNITED STATES PATENT OFFICE MEASURING ANDCONTROLLING APPARATUS Original application January 10, 1947, Serial No.721,242, now Patent No. 2,520,462, dated August Divided and thisapplication June 30, 1949, Serial No. 102,193

4 Claims. 1

The present invention is a division of my prior application, Serial No.721,242, filed January 10, 1947, now Patent No. 2,520,462 of August 29,1950, which relates to measuring apparatus of the balanceablepotentiometric type, and especially to improve means for maintainingsuch potentiometric measuring apparatus continuously standardized.

The present invention was primarily devised for use in measuringapparatus of the type in which minute uni-directional voltage variationsare converted into similar alternating voltage variations which mayreadily be amplified by electronic amplifying devices, and isparticularly well adapted for use with self-balancing potentiometricsystems to provide continuous automatic standardizing, assuring aconstant supply of energizing voltage to the potentiometric measuringcircuit at all times, and hence assuring highly accurate results inmeasurements made over extended periods of time.

A general object of the present invention is to provide an improvedconverter arrangement for converting uni-directional current intoalternating current.

According to the present invention, the converter arrangement comprisesa transformer having a primary winding on which the uni-directionalvoltage is impressed and having a secondary winding, and switching meansadapted to be operated by alternating current and operative toshort-circuit one half of the primary winding once during a portion onlyof the first half of each cycle of the alternating current, and toshort-circuit the other half of the primary winding once during aportion only of the second half of each cycle of the alternatingcurrent, for creating in the secondary winding of the transformer analternating voltage having a magnitude which is proportional to themagnitude of the uni-directional voltage, and having a frequency whichis twice that of the alternating current.

The various features of novelty which characterize this invention arepointed out with particularityin the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specific objects obtained with its use,reference should be had to the accompanying drawing and descriptivematter in which is illustrated and described a preferred embodiment of.the invention.

There is illustrated in the single figure of the drawing the circuitdiagram of a portion of a well-known form of self-balancingpotentiometric measuring apparatus of the type disclosed and claimed inthe Wills Patent 2,423,540. The apparatus illustrated in the drawingcomprises a potentiometric measuring circuit generally designated at I,a vibrating reed converter I00, an input transformer H2, and anelectronic voltage amplifier 4. These units operate together andcooperate with a power amplifier and motor drive circuit and with atwo-phase reversible rebalancing induction motor, not shown, to effectthe measurement of a minute uni-directional potential in a manner whichis described in my aforementioned prior patent and which is alsodescribed in detail in said Wills patent.

In the drawing, the potentiometric system is shown by way ofillustration as being connected to measure the instantaneous Values ofthe temperature of a thermocouple I. To this end, the potentiometriccircuit I includes a slide-wire resistance 9 having a sliding contactI0. The contact I0 is moved laterally by a suitable mechanical linkageI3 connected to the aforementioned rebalancing motor. The measuringsystem operates in a manner well known to those skilled in the art tocause the sliding contact I0 to be moved along the slide-wire resistance9 by operation of the motor so that the contact I0 is positionedaccording to the instantaneous temperatures of the thermocouple I.

In addition to the slide-wire resistance 9, the circuit I comprisesthree parallel-connected branches. The first of these is a measuringbranch, including three resistors I8, I9 and 20, connected in series.The slide-wire resistance 9 is connected in parallel with the resistorI9, the latter being located between the resistors I8 and 20. The secondparallel branch is an energizing branch including a battery 2I and avariable resistor 22, having a sliding contact 22A, connected in series.The third branch is a compensating branch, including a thermocouple coldjunction compensating resistor 23 and a standardizing resistor 24connected in series.

The converter I00 comprises a vibratile reed IOI which carries contactsI02 and I03, relatively stationary contacts I04, I 05, and I06, apermanent magnet I01, and an operating coil I08. The several contactsare so arranged in the converter I00 that the contacts I03 and I06 arein engagement whenever the contacts I02 and I04 are engaged, and thecontacts I03 and I06, and I02 and I04, are out of engagement wheneverthe contacts I02 and I 05 are engaged. In the manner described in myaforementioned prior patent, energization of the coil I08 withalternating curductor 12 to the sliding contact ill of the slide- I wireresistance 9. A point 15, constituting the junction between theconnected ends of the re'-' sisters 23 and 24 of the circuit i, isconnected to one end terminal of the primary winding we. The point isalso connected to the converter contact Hi l. The remaining end terminalof the primary winding I09 is connected to the converter contact I86 andto the remaining terminal of the thermocouple l by a conductor 14.

The electronic voltage amplifier may be of any suitable type, such asthe type disclosed in the aforementioned Wills patent. The amplifier tincludes input terminals 3!! and output terminals 36. and 3?, andenergizing terminals as and 39.

The secondary winding HG of the transformer l :2 is connected across theinput terminals 34. and 35 of the amplifier 4. The amplifier energizingterminals, 38 and 3.9, are connected by conductors 3| and 80 to asuitable source of alternating energizing current, not shown, ofsuitable frequency. Thisv frequency may, for example, be 60 cps. Theconverter operating coil [98 is adapted to be energized with alternatingcurrent from the same source which energizes the amplifier l.

The amplifier output terminals 35 and 3? are adapted to be connected tothe aforementioned unillustrated power amplifier and motor drivecircuit. The output of the latter is adapted to be connected to theaforementioned unillustrated reversible rebalancing motor whichpositions the contact 18 through the linkage l3. These components andinterconnections, are all illustrated and described in detail, in myaforementioned prior patent. When the slide-wire contact If} is in theposition along the slide-wire resistance 9 which corresponds to the theninstantaneous temperature of the thermocouple l, the potentiometricsystem is said to be balanced, and no voltage appears between thepotentiometric output terminal l5 and the output conductor l4.Consequently, no. input voltage is applied to the input transformer H2,and no signal is applied between the amplifier input terminals 34 and35. Under this condition, the, contact I0 is prevented from movingrelative to the slide-wire resistance 9 as long as the system remainsbalanced.

Upon a subsequent increase in the temperature of the thermocouple 1above the temperature value at which the system was balanced as justdescribed, the potentiometric circuit becomes unbalanced, and aunidirectional voltage appears in the output of the circuit l, betweenthe point I5 and the conductor 14, having a magnitude proportional tothe magnitude of the temperature increase and hence to the extent of thepotentiometric circuit unbalance, and having a given polaritycorresponding to a temperature increase. This voltage is alternatelyapplied across the input transformer primary winding [09, due to theoperation of the converter Hi9. Since the converter coil I08 is assumedto be energized with 60 cycle alternating voltage, the potentiometricunbalanced. Voltage is applied to the transformer primary winding H19during the first half of each cycle of the alternating supply voltage,but is short-circuited around the winding I08 by the action of thestationary contacts 104 and H15 and the cooperating reed contacts I02and 13 during the second half of each of said cycles, with the resultthat an alternating current signal is developed across the transformersecondary winding H0 having a magnitude proportional to the magnitude ofthe temperature increase and to the extent of the potentiometricunbalance, having a frequency of 6!! cycles per second, and having agiven phase corresponding to a temperature increase.

The signal just. described is applied to the input of the amplifier 4,wherein it is amplified, and the resulting signal is utilized to controlthe aforementioned amplifier and motor drive circuit as described in myprior patent mentioned above. The motor drive circuit then delivers tothe rebalancing motora signal of such phase and magnitude that the rotorof the motor is caused to rotate in such a manner as todrive the contactl0 along the slide-wire resistance 9 up scale or to the right in thedrawing to anew balance position corresponding to the new, increasedtemperature. When the contact In has been moved into this position, thesystem is once more balanced, and the motor rotor and contact m areprevented from further movement until a subsequent thermocoupletemperature change takes place.

Upon a subsequent decrease in the thermocouple temperature, the converseof what has just been described takes place. Specifically, aunidirectional voltage appears between the point i5 and the conductor I4having a magnitude proportional to the magnitude of the temperaturedecrease and having a polarity opposite to that corresponding to atemperature increase. By the conjoint action of the converter I00 andtransformer H2, this voltage is converted into a 60 cycle alternatingcurrent signal which appears between the amplifier input terminals 34and 35 having a magnitude proportional to the magnitude of thetemperature decrease, and being of opposite phase with respect to thecorresponding signal produced by a temperature increase. The signal isamplified by the amplifier 4 and is fed to. the motor drive circuit,which delivers to the rebalancing motor a signal of such phase andmagnitude that the motor is caused to drive the contact Ill down scaleor to the left in the drawing to a new balance position corresponding tothe new, decreased temperature. When the contact H! has moved to thisposition, the system is once more balanced, and the motor and contact inare prevented from further movement until a subsequent tempera turechange takes place.

The manner in which the apparatus herein described functions to performthe operations outlined above is described in detail in myaforementioned prior patent. and, in the aforementioned Wills Patent2,423,540, and hence no further description thereof will be, madeherein.

The continuous automatic standardizing apparatus of the illustratedarrangement comprises a standard cell 84, an input transformer H, theconverter I00, the amplifier 4, a suitable power amplifier and motordrive circuit not shown, a two-phase reversible standardizing motor, notshown, and a mechanical linkage 81'; The input transformer 1'! comprisesa core 11', two pri- 5 mary winding sections I8 and. I9 and a secondarywinding I6.

The rotor of the standardizing motor is :mechanically coupled by meansof the link 81 to the sliding contact 22A of the variable resistor 22,which is connected in the potentiometric circuit energizing branch. Thiscoupling is such that rotation of the standardizing motor in onedirection moves the contact 22A along the resistor 22 to increase theresistance of the latter, and hence, decreases the energizing currentflowing in the potentiometric circuit I. Rotation of the standardizingmotor in the opposite direction moves the contact 22A to decrease theresistance of the resistor 22, and hence, to increase the potentiometricenergizing current.

The input portion of the continuous automatic standardizing apparatus isconnected in a novel manner which causes the signal developed in thetransformer secondary winding IE to have a frequency of 120 cycles persecond, which is twice the frequency of the alternating voltage used toenergize the operating coil I08 of the converter I00.

For the purpose of causing the frequency of the voltage created in thesecondary winding I of the input transformer IT to have a frequencywhich is twice that of the alternating supply voltage, the convertercontact I04 is connected to one end terminal of the standardizing inputtransformer primary winding section I8 and to the point 15 of thepotentiometric measuring circuit I. The converter contact I05 isconnected to one end terminal of the transformer primary winding sectionI9 and to one terminal of the standard cell 84. The remaining terminalof the latter is connected to one end of the resistor 24, and theremaining end terminals of the transformer primary winding sections areconnected together and to the converter reed and contacts I02 and I03.

As shown, the transformer primary winding sections I8 and I9 of thestandardizing input transformer 11 are normally connected in series withthe standard cell 84 and the standardizing resistor 24. Any currentproduced by a need for standardizing will therefore flow through thewindings I8 and I9. However, as the converter contact I02 alternatelyengages the contacts I04 and I05, the windings I8 and I9 are alternatelyshort-circuited, each windin being so short-circuited once each cycle ofthe converter energizing voltage. Since the converter coil is energizedwith 60 cycle current, the short-circuiting of the two primary windingsI8 and I9 each cycle causes a 120 cycle signal to be produced in thesecondary winding I8 as a result of a need for standardizing.

The secondary winding I6 of the transformer is connected in series witha condenser II3 between the amplifier input terminals 34 and 35.Therefore, when both of the measuring and standardizing circuits aresimultaneously unbalanced, a complex signal is applied between the inputterminals 34 and 35. Therefore, when this occurs, a complex signal isapplied between the input terminals 34 and 35 consisting of a 60 cyclecomponent from the transformer H2 and the measuring circuit,representative of measuring circuit unbalance, and a 120 cycle componentfrom the transformer 11 and the standardizing circuit, representative ofstandardizing circuit unbalance. Due to the effect of the condenser II3,the I20 cycle standardizing signal component will be shifted in phasethrough 45 of the 6 60 cycle measuring signal component for a reason tobe described hereinafter.

When either the 60 cycle signal or the 120 cycle signal or both areapplied to the input of the amplifier 4, the amplified resultant of theinput signal will be applied to both the aforementioned measuring motordrive circuit and the aforementioned standardizing motor drive circuit.As described in detail in my aforementioned prior patent, the measuringmotor drive circuit is operative to produce a signal to cause operationof the associated rebalancing motor only in response to a 60 cycle inputsignal.

Consequently only a 60 cycle signal in the out put of the amplifier 4between the terminals 36 and 31 will cause operation of the rebalancingmotor, any 120 cycle signal, if present, having no effect on therebalancing motor. Therefore, the rebalancing motor operates solely inresponse to measuring circuit unbalance to effect rebalancing of thepotentiometric circuit I as previously brought out.

As fully described in my aforementioned prior patent, the standardizingmotor drive circuit is operative to effect rotation of the standardizingmotor only in response to a 120 cycle output signal from the amplifier 4which is shifted in phase 45 with respect to the supply voltage phase.Consequently, only such a 120 cycle signal will produce operation of thestandardizing motor, any 60 cycle signal, if [present in the output ofthe amplifier 4, having no effect on the operation of the standardizingmotor. Therefore, the standardizing motor drive circuit andstandardizing motor respond only to standardizing circuit unbalance toeffect rebalancing of the standardizing circuit and standardization ofthe potentiometric apparatus.

As is evident from the description of the apparatus previously given,the resistor 24 and the standard cell 84 are connected in series withthe primary winding sections I8 and I9 of the transformer TI. Thisconnection is made in such a manner that the voltage drop across theresistor 24 opposes the E. M. F. of the standard cell 84, so that whenthis voltage drop is just equal in magnitude to the standard cell E. M.F., no current flows in the transformer primary winding sections I8 andI9. Therefore, when the energizing current flowing in the circuit I andproduced by the battery 2I is of the correct value 'to produce thenormal voltage drop across the slide-wire resistance 9, no current flowsthrough the winding sections I8 and I9. Under this condition, thestandardizing circuit is balanced and the contact 22A is held stationaryon the resistor 22.

If the terminal voltage of the battery 2| decreases below the valueresponsible for the balanced condition of the standardizing circuit asjust described, the energizing current flowing in the circuit I willdecrease in magnitude and consequently the voltage drop across theresistor 24 will decrease. This voltage drop will now not be equal andopposite to the standard cell E. M. F., and hence a current will flow inthe transformer primary winding sections I8 and 19. This current throughthe sections I8 and I9 will be a pulsating one however, due to theperiodic shortcircuiting action of the converter contacts I02,

. I04 and I05.

input terminals 34v and tihaving a frequency of 120 cycles per second,having a magnitude proportional to the extent of the energizing currentdecrease, and being of a given phase corresponding to a decrease inpotentiometric energizing current and battery voltage.

The signal. applied to the input of the amplifier 2 is amplified thereinin the conventional manner and is applied to the input terminals of theaforementioned standardizing power amplifier and'motor drive circuit.The latter functions to produce in response to this signal a motor drivesignal which is applied to the standardizing motor. This drive signal isof such phase, and magnitude as to cause the standardizing motor torotate and to move the sliding contact 22A along the resistor 22 in adirection to decrease the effective resistance of the latter and henceto increase the potentiometer energizing current. The standardizingmotor will continue to thus drive the contact 22A to increase theenergizing current until the latter has once more reached its normalvalue. When this occurs, the voltage drop across the resistor 24 willonce more be equal and opposite to the standard cell E. M. F., no 120cycle signal will be applied to the amplifier 4,'the standardizingcircuit will again be balanced, and the contact 22A will be preventedfrom having further motion until a subsequent change takes place in thevoltage of the battery 2i. a

If the terminal voltage of the battery 2| should increase, thestandardizing system will function in such a manner that thestandardizing motor .will drive the contact 22A to increase theeffective resistance of the resistor 22 and hence decrease thepotentiometric energizing current. This will continue until theenergizing current is returned to its normal value and the standardizingcircuit is once more in balance.

From the description just given, it can be seen that the response of thestandardizing system to an unbalance of this system, due to a change inthe terminal voltage of the battery 2|, is analogous to the response ofthe potentiometric measuring system to an unbalance due to a change inthe temperature being measured by the thermocouple 1. Similarly, themanner in which the standardizing system functions to restore theenergizing current of the potentiometric system to its normal value, andhence to rebalance the standardizing system, is analagous to the mannerin which the potentiometric measuring system functions to restore thecondition of. zero potentiometric circuit output voltage, and hence torebalance the measuring system. It is to be noted, however, thatunbalance and rebalancing of the measuring system in no way affects thestandardizing system, and that rebalancing of the latter in no wayaffects the measurements made by or the operation. of the measuring.system. This latter statement is true since the standardizingv system isin continuous operation, and, therefore, any minute change in theterminal voltage of the battery 2| is compensated for by an adjustmentof the resistor 22 .before such a change can affect the accuracy of themeasurements made by the potentiometric .measuring system.

fier and a suitable source-of alternating current I as potentiometriccircuit energizing means.

While, in accordance with the provisions of the statutes, I haveillustrated and-described the best form of embodiment of the inventionnow known to me, it will be apparent to those skilled in the art thatchanges may be made in the form of the apparatusdisclosed withoutdeparting from the spirit of the invention as set forth 'in'the appendedclaims, and that in some cases certain features of the invention maysometimes be used to advantage without a corresponding use-of otherfeatures.

Having now described my invention, what I claim as new and desire tosecure with Letter Patent is: I

1. In combination, a transformer having a primary winding adapted tohave a unidirectional potential impressed thereacross and having asecondary winding, and switching means adapted to be operated byalternating current and operative to short-circuit one half of saidprimary winding once during a portion only of the first half of eachcycle of the alternating current and to short-circuit the other half ofsaid primary winding once during a portion only of the second half ofeach cycle of the alternating current, thereby to produce across saidsecondary winding an alternating potential having a magnitude which isproportional to that of the unidirectional potential, and having afrequency which is. twice that of the alternating current.

2. In combination, a transformer having two substantially identicalprimary windings and a secondary winding, a first pair of conductorsadapted to have a unidirectional potential produced therebetween,connections between said conductors and each of said primary windingswhereby the unidirectional potential between said conductors is normallyapplied to said primary windings, a second pair of conductors adapted tohave an alternating potential produced therebetween, and switching meansoperated by the alternating potential between said second pair ofconductors and adapted to shortcircuit one of said primary windings onceduring a portion only of the first half of each of the cycles of thealternating potential and to short-circuit the other of said primarywindings once during a portion only of the second half of each of thecycles of the alternating potential, thereby to cause an alternatingpotential to be produced across said secondary winding having amagnitude which is proportional to that of the unidirectional potentialand having a frequency which is twice that of thefirst mentionedalterhating potential.

3. In combination, a transformer having a primary winding adapted tohave a unidirectional potential produced thereacross and having asecondary winding, an electro-mechanical vibrating reed converter havingan operating coil adapted to be energized with alternating current andhaving a moving contact and two relatively stationary contacts, andconnections between said transformer and said converter whereby saidmoving contact and one of said stationary contacts cause one half ofsaid primary winding to be short-circuited once during a portion only ofthe first half of each cycle of the alternating current and whereby saidmoving contact and the other of said stationary contacts cause the otherhalf of said primary winding to be shortcircuited once during a portiononly of the second half of each cycle of the alternating current, said,connections being somade that an alterhating potential appears acrosssaid secondary winding having a magnitude which is proportional to theunidirectional potential, and having a frequency which is twice that ofthe alternating current.

4. In combination, a transformer having a primary winding adapted tohave a unidirectional potential produced thereacross and having asecondary winding, said primary winding also having an end terminal ateach end and a center-tap, an electro-mechanical, vibrating reedconverter having a, movable contact, two stationary contacts, and anoperating coil adapted to be energized with alternating current andoperative to move said movable contact into and out of engagement withone of said stationary contacts once during the first half of each cycleof the alternating current and to move said movable contact into and outof engagement with the other of said stationary contacts once during thesecond half of each cycle of the 10 alternating current, a connectionbetween one of said end terminals and said one stationary contact, aconnection between the other of said terminals and said other stationarycontact, and a connection between said center-tap and said movablecontact whereby an alternating potential is produced across saidsecondary winding having a magnitude which is proportional to that ofthe unidirectional potential and having a frequency which is twice thatof the alternating current.

CHARLES A. HARTUNG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Edwards June 8, 1948 Number

